1. Field of the Invention
The present invention relates to a defoaming apparatus for a foaming liquid, for example, an alkaline liquid after washing strips or the like, and specifically, it relates to a defoaming apparatus for defoaming by suctioning foam of a foaming liquid via a suction port of a casing by a rotation of an impeller in the casing and scattering the same by centrifugal force to collide against the inner circumferential surface of the casing.
2. Background Art
Priorly, as an apparatus for defoaming a foaming liquid by such a method, one as disclosed in Japanese Published Unexamined Patent Application No. H11-9903 has been known.
This prior art is for housing a foaming liquid in an open-type tank and defoaming foam of the foaming liquid by a defoaming unit provided on the tank. Illustration of an outline of the defoaming method is as shown in FIG. 7. In FIG. 7, A denotes a defoaming unit, and B denotes a foaming liquid housing tank. The defoaming unit A is provided with a casing C and an impeller D. E denotes a suction tube of the casing C in the defoaming unit A, F denotes a motor of the impeller D, and G denotes a discharge port of the casing C.
When the impeller D of the defoaming unit A is driven, air is suctioned into the casing C from the suction tube E and is discharged via the discharge ports G. In accordance therewith, foam on the liquid level of a foaming liquid in the tank B is suctioned into a casing C through the suction tube E. The suctioned foam is, by centrifugal force by a rotation of the impeller D, collided against the inner circumferential surface of the casing C and deformed. Liquid droplets generated by this defoaming fall from the discharge ports G into the tank B.
The tank B for housing a foaming liquid is an open type, and an inlet of the suction tube E is opened in a foam phase on the foaming liquid level in the tank B.
According to this prior art, an air flow produced by a rotation of the impeller D of the defoaming unit A is merely circulating in a relatively small region as shown by arrows in FIG. 7, therefore, a sufficient foam suctioning efficiency, that is, a sufficiently excellent defoaming efficiency cannot be expected. This is also apparent from the addition of modification such that the suction tube E is provided in plurality for the defoaming unit A, the suction tube E is made movable on the liquid level of the tank B, or foam on the liquid level of the tank B is raked up to the suction port of the suction tube by a scraper.